The invention relates generally to an adjustable seat back for a stroller, and more specifically to an adjustable seat back with side sections that fold inwardly to provide lateral support for a younger child or remain flat to provide a wider seat back for an older child.
A conventional stroller configuration (which is shown generally in FIG. 1) includes a seat having a back portion and a base portion, a push handle, and a pair of front and rear leg members. The front and rear legs are joined at a pivot point at one end and are fitted with wheels at the opposite end. The back portion of the seat and push handle are attached to the rear legs by a latch midway between the pivot point and the wheels.
The base and back portions of the seat usually consist of unisectional, nonadjustable cushions. The unisectional cushions are usually made generally planar and wide enough to accommodate a toddler. The width and planar aspects of these unisectional cushions can present a problem with the use of strollers by younger infants. By making the cushion wide enough to accommodate the larger child (a toddler), the cushions are often much wider than the children who are first beginning to use the stroller (a young baby or infant). Furthermore, infants often are not developed or coordinated sufficiently to sit up straight in the seat. Since the unisectional cushion provides no lateral support, the infant often tilts laterally, slumping sideways in the seat.
The foregoing problem could be alleviated by using a one-piece cushion which is contoured to fit the back of the youngest stroller user. However, this design would not be desirable since children tend to grow quickly, a stroller having a cushion which is contoured to fit an infant would soon become uncomfortable as the child grows. Thus, the effective length of use of a stroller having a contoured one-piece back would be unacceptably short. Consequently, it is desirable to provide a seat back that is adjustable between a narrow seat back for use by infants and a wide seat back for use by toddlers.
Several seat backs have been proposed that provide a method for narrowing the width of the seat back. U.S. Pat. No. 2,619,157 to Guyton et al. discloses an adjustable seat back for use by a pilot in an airplane. By rotating an adjusting knob that turns a threaded bar in a pair of threaded sleeves attached to the side panels, the side panels are moved laterally. Therefore, the pilot may incrementally adjust the width of the seat back by rotating the adjusting knob in the appropriate direction. Further, the side panels are attached to a split center section by a piano hinge and urged away from the occupant by a bungee cord so that when a release cable is pulled, the side panels open outward to release the pilot. However, the use of threaded bars, sprockets, and rotary knobs makes this a very complex design.
The adjustable automobile seat back disclosed in U.S. Pat. No. 4,913,491 to Mizuno et al., uses a pair of side supports, each of which are pivotable about a shaft and connected to each other by a transmission bar. By adjusting the transmission bar left or right, the user can simultaneously pivot both side supports inward or outward. Again, incorporation of the transmission bar and pivot shafts tends to make this a somewhat complex design.
Another adjustable seat back is disclosed in U.S. Pat. No. 3,608,960 to Sherman. This design includes two separately operated side supports that have a spring-urged ratchet mechanism so that when the occupant adjusts the side support, the ratchet mechanism retains the support in its adjusted position. The occupant must then push a release lever, disengaging the ratchet mechanism, to allow the side support to return to the plane of the central back section. Each of these side supports are individually operated so that the occupant must adjust and release each side support separately.
U.S. Pat. No. 5,022,709 to Marchino discloses an adjustable seat back that includes a flexible blade consisting of a convex central back portion and a pair of substantially flat side walls. When a load is applied to the flexible blade by the weight of the occupant, the central portion of the blade flexes so as to flatten the central portion and causes the ends of the central portion to move outward. Consequently, this causes the side walls to pivot about their respective hinges to produce a wrap-around effect. This design produces the opposite of the desired effect--the seat back remains wide under no (or light) load (e.g. an infant) and creates a wrap-around effect under a heavy load (e.g. a toddler).
Another adjustable seat back design is disclosed in U.S. Pat. Nos. 4,603,902; 4,653,805; and 4,696,514 all to Maloney. This design includes a stationary central back section and a pair of hinged side support sections. A latch member attached to each side support has a slot that engages a horizontal elongated bar when the side sections are coplanar with the central back portion. By pivoting the latch member 90 degrees to a horizontal orientation and manually pulling the side section away from the elongated bar, the corner portion of the latch member engages a slot in the elongated bar to hold the side section in the extended position. Thus, this design requires that each side support be adjusted separately.